Re: [PATCH] security, crypto: LLVMLinux: Remove VLAIS from ima_crypto.c

From: Behan Webster
Date: Sat Sep 06 2014 - 22:06:36 EST

On 09/06/14 03:11, Thomas Gleixner wrote:
On Fri, 5 Sep 2014, Behan Webster wrote:
On 09/05/14 17:18, Thomas Gleixner wrote:
Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Mark Charlebois <charlebm@xxxxxxxxx>
Signed-off-by: Jan-Simon MÃller <dl9pf@xxxxxx>
This SOB chain is completely ass backwards. See Documentation/...
"The Signed-off-by: tag indicates that the signer was involved in the
development of the patch, or that he/she was in the patch's delivery path."

All three of us were involved. Does that not satisfy this rule?
No. Read #12

The sign-off is a simple line at the end of the explanation for the
patch, which certifies that you wrote it or otherwise have the right to
pass it on as an open-source patch.

So the above chain says:

Written-by: Behan
Passed-on-by: Mark
Passed-on-by: Jan

That would be correct if you sent the patch to Mark, Mark sent it to
Jan and Jan finally submitted it to LKML.
I suppose "Reviewed-by" is probably more appropriate for the last 2 then. Will fix.

- struct {
- struct shash_desc shash;
- char ctx[crypto_shash_descsize(tfm)];
- } desc;
+ char desc[sizeof(struct shash_desc) +
+ crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR;
+ struct shash_desc *shash = (struct shash_desc *)desc;
That anon struct should have never happened in the first place.
Sadly this is a design pattern used in many places through out the kernel, and
appears to be fundamental to the crypto system. I was advised *not* to change
it, so we haven't.

I agree that it's not a good practice.

your problem, but you are not making it any better. You replace open
coded crap with even more unreadable crap.

Whats wrong with

SHASH_DESC_ON_STACK(shash, tfm);
Nothing is wrong with that. I would have actually preferred that. But it would
have fundamentally changed a lot more code.
Errm. Why is

#define SHASH_DESC_ON_STACK(shash, tfm) \
char __shash[sizeof(.....)]; \
struct shash_desc *shash = (struct shash_desc *) __shash

requiring more fundamental than open coding the same thing a gazillion
times. You still need to change ALL usage sides of the anon struct.

So in fact you could avoid the whole code change by making it


and do the anon struct or a proper struct magic in the macro.
I see. I thought you meant a more fundamental change to the crypto system API. My misunderstanding.

Ironically we tried to stay away from macros since the last time we tried to replace VLAIS using macros (we've attempted patches to remove VLAIS a few times) we were told *not* to hide the implementation with macro magic. Though, to be fair, we were using more pointer math in our other macro-based effort, and the non-crypto uses of VLAIS are a lot more complex to replace.

Like I said I'm actually a fan of hiding ugliness in macros. Will fix.

Again, thanks for the feedback,


Behan Webster

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